Compressed-air braking system for a motor vehicle

Abstract

A compressed-air braking system (DBA*) for a motor vehicle, includes a compressed-air supply device (1) with a compressor (2) and several brake circuits which are connected to the compressed-air supply device (1) via a multi-circuit protection valve (7) and include at least one parking brake circuit with parking brake cylinders (25.1, 25.2). In order to reduce the operating noise of the compressed-air braking system (DBA*) occurring in particular on venting of the parking brake cylinders (25.1, 25.2), it is provided that the parking brake cylinders (25.1, 25.2) can be vented, per wheel or per vehicle axle, alternately either to the surrounding atmosphere or into an additional reservoir (31) via a respective quick-venting valve (29) connected to a connecting line (28) and a changeover valve (30) arranged downstream thereof.

The invention claimed is: 
     
       1. A compressed-air braking system (DBA*) for a motor vehicle, the compressed-air braking system comprising:
 a compressed-air supply device ( 1 ) with a compressor ( 2 ) and 
 several brake circuits which are connected to the compressed-air supply device ( 1 ) via a multi-circuit protection valve ( 7 ), and include at least one parking brake circuit with parking brake cylinders ( 25 . 1 ,  25 . 2 ), 
 wherein the parking brake cylinders ( 25 . 1 ,  25 . 2 ) are configured to be vented, per wheel or per vehicle axle, alternately either to the surrounding atmosphere or into a reservoir ( 31 ) via a respective quick-venting valve ( 29 ) connected to a connecting line ( 28 ) and a changeover valve ( 30 ) arranged downstream thereof in the at least one parking brake circuit. 
 
     
     
       2. The compressed-air braking system as claimed in  claim 1 , wherein the quick-venting valve ( 29 ) comprises an input port ( 35 ), a working port ( 36 ) and an output port ( 37 ),
 wherein the input port ( 35 ) is connected via a pressure line ( 27 ) to the output port of a relay valve ( 24 ) controlled by a handbrake valve ( 23 ), wherein the working port ( 36 ) is connected via the connecting line ( 28 ) to the parking brake cylinders ( 25 . 1 ,  25 . 2 ), and wherein the output port ( 37 ) is connected via an output line ( 38 ) to an input port ( 40 ) of the changeover valve ( 30 ). 
 
     
     
       3. The compressed-air braking system (DBA*) for a motor vehicle, the compressed-air braking system comprising:
 a compressed-air supply device ( 1 ) with a compressor ( 2 ) and 
 several brake circuits which are connected to the compressed-air supply device ( 1 ) via a multi-circuit protection valve ( 7 ), and include at least one parking brake circuit with parking brake cyliners ( 25 . 1 ,  25 . 2 ), 
 wherein the parking brake cylinders ( 25 . 1 ,  25 . 2 ) are configured to be vented, per wheel or per vehicle axle, alternately either to the surrounding atmosphere or into a reservoir ( 31 ) via a respective quick-venting valve ( 29 ) connected to a connecting line ( 28 ) and a changeover vale ( 30 ) arranged downstream thereof in the at least one parking brake circuit, and 
 wherein the changeover valve ( 30 ) is configured as a pressure-controlled 3/2-way directional valve with a control pressure input ( 39 ), an input port ( 40 ) and two output ports ( 41 ,  42 ), the 3/2-way directional valve having an unactuated rest state, in which the input port ( 40 ) is connected to the first output port ( 41 ), and a switched state, in which the input port ( 40 ) is connected to the second output port ( 42 ), wherein the control pressure input ( 39 ) is connected to the input port ( 40 ), the first output port ( 41 ) leads to the surrounding atmosphere, and the second output port ( 42 ) is connected to the reservoir ( 31 ). 
 
     
     
       4. The compressed-air braking system as claimed in  claim 3 , wherein the changeover valve ( 30 ) has a valve spring ( 44 ) with at least a spring stiffness or a set preload, dimensioned such that the input port ( 40 ) is connected to the first output port ( 41 ) below a predefined changeover pressure (p S ) present at the control pressure input ( 39 ), and to the second output port ( 42 ) on reaching or exceeding of the changeover pressure (p S ). 
     
     
       5. The compressed-air braking system as claimed in  claim 4 , wherein the changeover pressure (p S ) of the changeover valve ( 30 ) is set to a value above which outflowing compressed air in the narrowest cross-section of an air outlet of the parking brake cylinders ( 25 . 1 ,  25 . 2 ) reaches the speed of sound. 
     
     
       6. The compressed-air braking system as claimed in  claim 5 , wherein the changeover pressure (p S ) of the changeover valve ( 30 ) is set to a value in the range of 1.9×10 5  Pa through 2.5×10 5  Pa. 
     
     
       7. The compressed-air braking system as claimed in  claim 4 , wherein the narrowest cross-section of the air outlet at the first output port ( 41 ) of the changeover valve ( 30 ) is larger by a factor of 1.1 to 2.5 than the narrowest cross-section of an air outlet of an associated parking brake cylinder ( 25 . 1 ,  25 . 2 ). 
     
     
       8. The compressed-air braking system as claimed in  claim 1 , wherein the reservoir ( 31 ) is connected via a connecting line ( 32 ) to an intake tank ( 33 ) of the compressor ( 2 ), and wherein a check valve ( 34 ), which blocks an air flow into the surrounding atmosphere, is arranged in a suction line ( 43 ) connecting the intake tank ( 33 ) to the environment. 
     
     
       9. The compressed-air braking system as claimed in  claim 1 , wherein the parking brake cylinders ( 25 . 1 ,  25 . 2 ) connected to the quick-venting valve ( 29 ) and the changeover valve ( 30 ) are configured to be arranged on a trailerless motor vehicle, or on a trailer vehicle, or on a rear part of an articulated bus. 
     
     
       10. A compressed-air braking system (DBA*) for a motor vehicle, the compressed-air braking system comprising:
 a compressed-air supply device ( 1 ) with a compressor ( 2 ) and 
 several brake circuits which are connected to the compressed-air supply device ( 1 ) via a multi-circuit protection valve ( 7 ), and include at least one parking brake circuit with parking brake cylinders ( 25 . 1 ,  25 . 2 ), 
 a quick-venting valve ( 29 ) connected to the parking brake cylinders ( 25 . 1 ,  25 . 2 ) and configured to vent the parking brake cylinders, 
 a changeover valve ( 30 ) downstream from the quick-venting valve ( 29 ) and connected to the quick-venting valve ( 29 ) via an output line ( 38 ) therefrom, 
 a reservoir ( 31 ) downstream from the changeover valve ( 30 ), 
 wherein the parking brake cylinders ( 25 . 1 ,  25 . 2 ) are configured to be vented, per wheel or per vehicle axle, to both the surrounding atmosphere and into the reservoir ( 31 ) via the changeover valve ( 30 ), 
 wherein the parking brake cylinders ( 25 . 1 ,  25 . 2 ) vent to either the surrounding atmosphere or into the reservoir depending on a pressure level at the changeover valve ( 30 ). 
 
     
     
       11. The compressed-air braking system as claimed in  claim 10 , wherein the quick-venting valve ( 29 ) comprises an input port ( 35 ), a working port ( 36 ) and an output port ( 37 ),
 wherein the input port ( 35 ) is connected via a pressure line ( 27 ) to the output port of a relay valve ( 24 ) controlled by a handbrake valve ( 23 ), wherein the working port ( 36 ) is connected via a connecting line ( 28 ) to the parking brake cylinders ( 25 . 1 ,  25 . 2 ), and wherein the output port ( 37 ) is connected via the output line ( 38 ) to an input port ( 40 ) of the changeover valve ( 30 ). 
 
     
     
       12. The compressed-air braking system as claimed in  claim 10 , wherein the changeover valve ( 30 ) is configured as a pressure-controlled 3/2-way directional valve with a control pressure input ( 39 ), an input port ( 40 ) and two output ports ( 41 ,  42 ), the 3/2-way directional valve having an unactuated rest state, in which the input port ( 40 ) is connected to the first output port ( 41 ), and a switched state, in which the input port ( 40 ) is connected to the second output port ( 42 ), wherein the control pressure input ( 39 ) is connected to the input port ( 40 ), the first output port ( 41 ) leads to the surrounding atmosphere, and the second output port ( 42 ) is connected to the reservoir ( 31 ). 
     
     
       13. The compressed-air braking system as claimed in  claim 12 , wherein the changeover valve ( 30 ) has a valve spring ( 44 ) with at least a spring stiffness or a set preload, dimensioned such that the input port ( 40 ) is connected to the first output port ( 41 ) below a predefined changeover pressure (p S ) present at the control pressure input ( 39 ), and to the second output port ( 42 ) on reaching or exceeding of the changeover pressure (p S ). 
     
     
       14. The compressed-air braking system as claimed in  claim 13 , wherein the changeover pressure (p S ) of the changeover valve ( 30 ) is set to a value above which outflowing compressed air in the narrowest cross-section of an air outlet of the parking brake cylinders ( 25 . 1 ,  25 . 2 ) reaches the speed of sound. 
     
     
       15. The compressed-air braking system as claimed in  claim 14 , wherein the changeover pressure (p S ) of the changeover valve ( 30 ) is set to a value in the range of 1.9×10 5  Pa through 2.5×10 5  Pa. 
     
     
       16. The compressed-air braking system as claimed in  claim 13 , wherein the narrowest cross-section of the air outlet at the first outport port ( 41 ) of the changeover valve ( 30 ) is larger by a factor of 1.1 to 2.5 than the narrowest cross-section of an air outlet of an associated parking brake cylinders ( 25 . 1 ,  25 . 2 ). 
     
     
       17. The compressed-air braking system as claimed in  claim 10 , wherein the reservoir ( 31 ) is connected via a connecting line ( 32 ) to an intake tank ( 33 ) of the compressor ( 2 ), and wherein a check valve ( 34 ), which blocks an air flow into the surrounding atmosphere, is arranged in a suction line ( 43 ) connecting the intake tank ( 33 ) to the environment. 
     
     
       18. The compressed-air braking system as claimed in  claim 10 , wherein the parking brake cylinders ( 25 . 1 ,  25 . 2 ) connected to the quick-venting valve ( 29 ) and the changeover valve ( 30 ) are configured to be arranged on a trailerless motor vehicle, or on a trailer vehicle, or on a rear part of an articulated bus.